Scanning Acoustical Microscopy (also referred to as SAM and C-SAM) is a method of non-destructive inspection used for identifying buried interfaces of dissimilar materials. SAM can be used to examine the internal structure of many solid materials but is particularly useful in the examination of electronic components. An ultra high frequency sound wave is sent through the material or IC package to identify delaminations/voids between package interfaces at the die, die paddle, and leadframe.

At one time plastic IC’s had reliability problems as they could not adequately handle temperature cycling, and as a result, were likely to absorb moisture. This internal moisture would generally find it’s way to an internal defect, such as a delamination, and become steam as the device went through wave-soldering, thus leading to chip cracking, wire-bond breaks, or even plastic cracking.

Additionally, new, larger IC chips with many IO’s generate an even greater amount of heat. It is extremely important that the conductive epoxy bonding the chip in place have no voids or air gaps so that heat transfer to the substrate can efficiently take place.

Scanning Acoustical Microscopy is an effective tool to determine if there are any gaps or voids or delaminations, for any of these types of defects will reflect the ultrasound back to a detector and produce an image of the slice of the device being evaluated.